Preheat the Cooking Surface: Preheat a griddle or skillet over medium heat, then grease the surface well with butter.
Prepare the Pumpkin Batter: Add the eggs, canned pumpkin, milk, light brown sugar, flour, salt, vanilla extract, cinnamon, pumpkin pie spice, and ground nutmeg to a shallow dish or blender. Whisk the mixture until the batter is smooth and well combined. Coat the Bread: Dip each thick slice of bread into the pumpkin batter, turning it so both sides are evenly coated.
Cook the French Toast: Place the coated bread onto the hot, greased griddle or skillet.Cook for a few minutes, until the underside is browned. Flip the Slices: Carefully turn each slice over and continue cooking until the second side is browned and the French toast is cooked through.
Serve Warm: Transfer the finished French toast to serving plates and serve warm with syrup and powdered sugar.